1. Field of the Invention
The present invention relates to a mounting structure of an impact absorbing pad which is mounted to a back surface of an interior lining such as a door lining or the like, and particularly relates to a mounting structure of an impact absorbing pad which makes it possible to facilitate positioning and fixing of the impact absorbing pad by providing a holder integrated with the lining at a mounting reference position of the impact absorbing pad, and is enhanced in durability of the impact absorbing pad without breakage of the impact absorbing pad owing to the holder even if an impact load is applied from a lateral direction of an indoor side of a vehicle at a time of side collision or the like.
2. Description of the Related Arts
The interior lining mounted to the indoor side of the side wall panel of a vehicle normally includes an impact absorbing function capable of absorbing an impact load applied to a passenger when an impact is applied from a side. For example, a door lining 1 shown in FIG. 9A satisfies the function of the door lining 1 by a door lining body 1a being formed into a predetermined shape by mold-press forming, or injection-molding a synthetic resin such as a PP (polypropylene) resin or the like and providing an arm rest 1b, a door pocket 1c and a speaker grill 1d to be integrated with the door lining body 1a or separately from the door lining body 1a. 
On the back surface of the door lining body 1a in the door lining 1, an impact absorbing pad 2 is bonded and fixed to a location corresponding to, for example, a waist of a passenger by a hot-melt adhesive or the like, as a waist impact area as shown in FIG. 9B. As the impact absorbing pad 2, polyurethane foam, polystyrene foam and the like which are molded are conventionally used.
Recently, attention is given to a method for mounting the impact absorbing pad 2 by mechanical fixing in order to position the impact absorbing pad 2 at a predetermined location of the back surface of the door lining body 1a quickly and enhance operability. For example, as shown in FIG. 10, as a method for mechanically fixing the impact absorbing pad 2 at three fixing points, a box-shaped holder 3 is vertically provided at a mounting reference position at the back surface of the door lining body 1a, and mounting bosses 4 are projectingly formed at the remaining two fixing points.
Then, an insertion piece 5 of the impact absorbing pad 2 is inserted into an opening 3a of the box-shaped holder 3, and fixation of the impact absorbing pad 2 at the mounting reference position is carried out. Thereafter, the mounting bosses 4 are inserted into mounting holes 6a of mounting pieces 6 symmetrically formed at a left and a right sides of the impact absorbing pad 2, and tip ends 4a of the mounting bosses 4 are ultrasonically crimped, whereby, the impact absorbing pad 2 is fixed at three points that are the box-shaped holder 3 and two ultrasonic fixing points in the predetermined location of the back surface of the door lining body 1a as shown in FIG. 11 to FIG. 13. Accordingly, the insertion piece 5 of the impact absorbing pad 2 has the construction in which a top surface 5a and three side surfaces 5b abut on and are supported by an inside of the box-shaped holder 3, as shown, for example, in Japanese Patent Application Laid-open No. 2003-252155.
The bonding and fixing structure which is conventionally adopted as the structure for mounting the impact absorbing pad 2 to the back surface of the door lining body 1a has the disadvantages that positioning of the impact absorbing pad 2 is troublesome and a long operation time is required for a coating step, a drying step and the like of the adhesive. On the other hand, the mechanical fixing structure which uses the box-shaped holder 3 and the mounting bosses 4 can solve these disadvantages, and has the advantages of facilitating positioning and requiring a short operation time.
However, in the structure using the box-shaped holder 3, the construction in which the box-shaped holder 3 supports the insertion piece 5 so as to wrap the insertion piece 5 is adopted, and therefore, the disadvantages that a fitting operation is complicated because the sectional area of the opening 3a of the box-shaped holder 3 and the sectional area of the insertion piece 5 are set to be substantially the same; and when the knee of a passenger hits the door lining 1 and an impact is applied from the lateral direction of the indoor side of the vehicle, a load especially concentrates on the impact absorbing pad 2 from an edge part 3c of a top plate part 3b of the box-shaped holder 3, the impact absorbing pad 2 is broken and falls off, and the impact absorbing function of the impact absorbing pad 2 cannot be fully performed at the time of collision are pointed out.